This invention relates in general to bearings and more particularly to a bearing together with a stiffened axle journal which experiences less fretting in operation.
Most rail cars used by railroads in the United States rely on antifriction bearings to reduce friction and thereby lessen the tractive effort required to move such cars. Typically, the wheels of such cars are fitted to axles with which they rotate. Each axle extends beyond its wheels in the form of journals that are of a lesser diameter than the remainder of the axle. The bearings fit snugly over the journals and into housings which in turn are received in side frames for a truck. Being the thinnest portion of the axle and at the locations where the weight of the rail car is transferred to the axle, the journals tend to flex as the rail car moves over the rails, at least when the rail car is heavily loaded.
The flexure is perhaps most pronounced at the inboard end of each bearing. Here the typical journal is fitted with a seal wear ring that extends between the inner race of the bearing and a backing ring which fits over a fillet located where the journal merges into a larger adjoining portion of the axle often referred to as the dust guard portion. The wear ring provides a cylindrical surface around which a seal fits to retain lubrication within the bearing and to prevent the entry of contaminants. Both the inner race and the wear ring, at least where the wear ring abuts the inner race, fit snugly over the journal. By reason of the flexure in the journal, fretting occurs between the journal, on one hand, and the inner race and inboard wear ring on the other.
The fretting erodes the journal and thereby produces a looser fit between the inner race and wear ring and the journal. This looser fit compounds the fretting. In severe cases the fretting can lead to overheating and bearing distress. Moreover, the axle is weakened, and the effectiveness of the seal is diminished, because the wear ring around which it is fitted does not remain concentric with the journal.
To be sure, others have addressed the fretting problem along the journals of rail car axles. These efforts have included increasing the surface hardness of the axle journal, increasing the surface area of the wear ring in contact with the journal and even separating the wear ring entirely from the surface of the journal by using the backing ring to center it with regard to the journal instead of the journal itself. All have increased the cost of the bearing or its installation.
The present invention resides in the combination of a bearing and axle journal which thwarts fretting along the journal. Seals, which close the ends of the bearing, are fitted to and operate along the races of the bearing thus eliminating the wear rings. This in turn shortens the journal, making it stiffer. Indeed, the inner race is located about where the journal fillet begins, so the location where fretting is traditionally the greatest is in a very stiff region of the journal--a region where flexure is minimum. The invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.